In a given generation of products, the embedded electronics manufacturer strives to design for compatibility with both legacy products as well as the newest, highest performance products of the future. This gives the best product flexibility and usefulness to the widest range of customers. To attain these goals, it is desirable for baseboards that support mezzanine cards to be designed to support multiple generations of mezzanine cards whose bus interfaces to the baseboard require different operating voltages or different signaling voltages. Most prior art implementations utilize a physical keying mechanism so that only mezzanine cards with compatible operating voltages can interface with the baseboard. This prevents damage to the baseboard, mezzanine card and the entire computer system. Thus, the baseboard must be configured differently for each mezzanine card operating voltage.
Two types of configuration implementations exist in prior art. In the first, the operating voltage supplied to a given mezzanine card interface is set during the manufacture of the baseboard. Through the appropriate population of onboard components, a preset operating voltage is routed to each mezzanine card interface and the physical keying mechanism is attached in the corresponding position. Through a different population of onboard components and a different physical key position, a different preset operating voltage can be routed to each mezzanine card interface. This allows one baseboard design to support mezzanines with different operating voltage requirements. A disadvantage of this method is that it is not field-reconfigurable for other mezzanine cards with different operating voltages.
In the second implementation, the operating voltage supplied to a given mezzanine card interface is set in a way that is field-reconfigurable, such as using jumpers. Thus, to change a mezzanine interface from one operating voltage to another, a user would be required to:
1) Change the jumper position to select a different operating voltage, and
2) Move the physical keying mechanism to the corresponding position. A disadvantage of this method is that it allows the possibility of incompatible configurations with no fault protection. For example, a user could install the physical key in a position that does not match the jumper-selected operating voltage, in which case the wrong operating voltage might be applied to the mezzanine card, causing damage. Accordingly, there is a significant need for an apparatus and method that overcomes the disadvantages of the prior art outlined above.
It will be appreciated that for simplicity and clarity of illustration, elements shown in the drawing have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to each other. Further, where considered appropriate, reference numerals have been repeated among the Figures to indicate corresponding elements.